Datasheet

MAX3301E/MAX3302E
USB On-the-Go Transceivers and Charge Pumps
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Detailed Description
The USB OTG specification defines a dual-role USB
device that acts either as an A device or as a B device.
The A device supplies power on V
BUS
and initially
serves as the USB host. The B device serves as the ini-
tial peripheral and requires circuitry to monitor and pulse
V
BUS
. These initial roles can be reversed using HNP.
The MAX3301E/MAX3302E combine a low- and full-
speed USB transceiver with additional circuitry required
by a dual-role device. The MAX3301E/MAX3302E
employ flexible switching circuitry to enable the device
to act as a dedicated host or peripheral USB transceiv-
er. For example, the charge pump can be turned off and
the internal regulator can be powered from V
BUS
for
bus-powered peripheral applications.
The Selector Guide shows the differences between the
MAX3301E and MAX3302E. The MAX3301E powers up
in its lowest power state and must be turned on by set-
ting the sdwn bit to 0. The MAX3302E powers up in the
operational, VP/VM USB mode. This allows a micro-
processor (µP) to use the USB port for power-on boot-
up, without having to access I
2
C. To put the MAX3302E
into low-power shutdown, set the sdwn bit to 0. In the
MAX3302E, special-function register 2 can be
addressed at I
2
C register location 10h, 11h (as well as
locations 16h, 17h) to support USB OTG serial-interface
engine (SIE) implementations that are limited to I
2
C
register addresses between 0h and 15h.
Transceiver
The MAX3301E/MAX3302E transceiver complies with
the USB version 2.0 specification, and operates at full-
speed (12Mbps) and low-speed (1.5Mbps) data rates.
Set the data rate with the SPD input. Set the direction of
data transfer with the OE/INT input. Alternatively, control
transceiver operation with control register 1 (Table 7)
and special-function registers 1 and 2 (see Tables 14,
15, and 16).
Level Shifters
Internal level shifters allow the system-side interface to
run at logic-supply voltages as low as +1.65V. Interface
logic signals are referenced to the voltage applied to
the logic-supply voltage, V
L
.
Charge Pump
The MAX3301E/MAX3302E’s OTG-compliant charge
pump operates with +3V to +4.5V input supply voltages
(V
CC
) and supplies a +4.8V to +5.25V OTG-compatible
output on V
BUS
while sourcing the 8mA or greater out-
put current that an A device is required to supply.
Connect a 0.1µF flying capacitor between C+ and C-.
Bypass V
BUS
to GND with a 1µF to 6.5µF capacitor, in
accordance with USB OTG specifications. The charge
pump can be turned off to conserve power when not
used. Control of the charge pump is set through the
vbus_drv bit (bit 5) of control register 2 (see Table 8).
Linear Regulator (TRM)
An internal 3.3V linear regulator powers the transceiver
and the internal 1.5kΩ D+/D- pullup resistor. Under the
control of internal register bits, the linear regulator can be
powered from V
CC
or V
BUS
. The regulator power-supply
settings are controlled by the reg_sel bit (bit 3) in special-
function register 2 (Tables 15 and 16). This flexibility
allows the system designer to configure the MAX3301E/
MAX3302E for virtually any USB power situation.
The output of the TRM is not a power supply. Do not use
as a power source for any external circuitry. Connect a
1.0µF (or greater) ceramic or plastic capacitor from TRM
to GND, as close to the device as possible.
V
BUS
Level-Detection Comparators
Comparators drive interrupt source register bits 0, 1,
and 7 (Table 10) to indicate important USB OTG V
BUS
voltage levels:
•V
BUS
is valid (vbus_vld)
• USB session is valid (sess_vld)
• USB session has ended (sess_end)
The vbus_valid comparator sets vbus_vld to 1 if V
BUS
is
higher than the V
BUS
valid comparator threshold. The
V
BUS
valid status bit (vbus_vld) is used by the A device
to determine if the B device is sinking too much current
(i.e., is not supported). The session_valid comparator
sets sess_vld to 1 if V
BUS
is higher than the session
valid comparator threshold. This status bit indicates that
a data transfer session is valid. The session_end com-
parator sets sess_end to 1 if V
BUS
is higher than the
Figure 12. Comparator Network Diagram
V
BUS
VBUS_VLD
V
TH-VBUS
V
TH-SESS_VLD
V
TH-SESS_END
SESS_VLD
SESS_END